go-air install

refer： https://github.com/cosmtrek/air/blob/master/README.md

如果使用asdf go无法安装air,可以使用sh方法：（有效）

# binary will be $(go env GOPATH)/bin/air
curl -sSfL https://raw.githubusercontent.com/cosmtrek/air/master/install.sh | sh -s -- -b $(go env GOPATH)/bin
# or install it into ./bin/
curl -sSfL https://raw.githubusercontent.com/cosmtrek/air/master/install.sh | sh -s
air -v

然后就可以启动go项目了。